Author: blass uri
Date: 03:25:00 03/06/00
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On March 06, 2000 at 06:00:20, Jan Pernicka wrote: >On March 03, 2000 at 15:53:31, blass uri wrote: > >>Suppose you have a program with evaluation of 0.00 for every position so the >>order of moves is always perfect. >>Suppose this program does no prunning and no extensions. >> >>What is the branching factor of this program and how many nodes does it need to >>search to get 17 plies in the positions that deeper blue is supposed to get 17 >>plies with no prunning and a lot of extensions? >> >>It seems to me that it is impossible with no hash tables to get 17 plies in 3 >>minutes even if you can search 200,000,000 nodes/second,have a perfect order of >>moves and do no extensions. >> >>Hash tables can help to reduce the branching factor but how much do they help? >> > > Hi, >let's suppose that at every position you have w moves to choose and you >don't use any hashtables. Then (it's well known) - when using alpha-beta >prunning - your branching factor is something like sqrt(w) - i.e square >root, when searching to the depth d (still the same, no extensions...), >you have to examine about d^(w/2) (leaf) positions (x^y means "x powered to >y"), so you can estimate how long does it take (for your program) to search >17 plies ahead... Simply said - you can search two times deeper... I think that the formula is sqrt(w)^d=w^(d/2) If w=36 in the middle game then the formula is 6^d without hastables and f(w)^d with the hashtables when the question is if f(w) is really close to 6. If f(w) is really close to 6 then the claim that deeper blue could search 17 plies in the middle game with no pruning is wrong. Uri
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